Add URL fragment -> client-side search

[jashkenas]

Per: https://github.com/jashkenas/underscore/issues/2019

It would be lovely to add a little client-side magic to the docco templates, so that you would be able to use a specially crafted URL fragment to jump to a matching location on the page.

This could be used to automatically link to documentation for a given function, or whatever.

docs.html#find/_.template